J . Org. Chem. 1995,60, 4595-4601
4595
Stereoselective Synthesis of 1,4-Dienes. Application to the Preparation of Insect Pheromones (32,62)-Dodeca-3,6-dien-l-o1 and (4E,72)-Trideca-4,7-dienyl Acetate Michael W. Hutzinger and Allan C. Oehlschlager" Department of Chemistry, Simon Fraser University, B u r n a b y , B.C., V5A 1S6, C a n a d a Received January 13, 1995@
Stereoselective synthesis of 23- and 2,Z-1,kdienes has been achieved by the cross-coupling of allylic substrates with vinyl organometallic reagents. Key to this strategy was the development of a method for regiospecific incorporation of a tri-n-butylstannyl group in the y-position of the allylic cross-coupling partner. The steric bulk of this moiety ensures the stereochemical integrity of the allylic double bond throughout the coupling sequence and is easily replaced by hydrogen in the coupled product. This strategy has been applied to the synthesis of the termite trail marker pheromone 22 and the leafminer moth sex pheromone 28.
Introduction Since the first pheromone was identified from the silk worm moth Bombyx mori by Butenandt et al. in 1961,l a vast array of these semiochemicals have been identified.2 The availability of high purity synthetic pheromones has allowed use of these behavior modifying chemicals in pest management. Most Lepidopteran pheromones are linear alcohols, aldehydes, or acetates containing one or more double bonds. It is the strict maintenance of double bond geometry which often conveys biological activity and presents the greatest difficulty in preparation. Increasing demand for pheromones of high isomeric purity has spurred development of improved syntheses of these behavior modifying ~ h e m i c a l s . ~ In connection with ongoing projects in our laboratory dealing with characterization and synthesis of insect pheromones, new methods have been developed which would allow stereoselective assembly of 1,5-disubstituted 1,Cdienes which are structural units commonly found in a multitude of biologically active molecules including pheromones. Common methods to stereoselectively assemble 1,4dienes are (a) reduction of 1,kdiynes or 1,4-enynes by catalytic hydrogenation4" or reduction with sodium in liquid a m m ~ n i a ; (b) ~ ~ coupling .~ of carbonyl compounds with ylides in Wittig and related reactions5 and (c) organometallic mediated reactions.6 Palladium(0) catalyzed cross-coupling of vinyl organometallics as well as direct coupling of vinyl cuprates with allylic substrates are well established stereoselective routes to 1 , 4 - d i e n e ~ .Stereochemistry ~ of the vinyl partner is maintained in these reactions, but regio- and @Abstractpublished in Advance ACS Abstracts, July 1, 1995. (1)Butenandt, A,; Beckman, R.; Hecker, E.; Stamm, D. J . Physiol. Chem. 1961,324,71. (2)Jacobson, M. In Insecticides of the Future; Marcel Dekker: New York, 1975. (3)For reviews see: (a)Henrick, C. A. Tetrahedron 1977,33,1845. (b) Rossi, R.Synthesis 1977,817.(c) Mori, K.The Synthesis of Insect Pheromones. In The Total Synthesis of Natural Products; ApSimon, J., Ed.; Wiley: New York, 1981. (4)For representative examples see: (a) Prestwich G. D.; Carvalho, (b)Yadav, J. S.; Reddy, P. S. Synth. J . F. J . Org. Chem. 1984,49,1251. Commun. 1986,16, 1119.( c ) Vig, 0. P.; Sharma, M. L.; Kumari, S.; Rani, V. Indian J . Chem. 1986, 24B,675. (5) For a representative example see: Bestmann, H. T.; Vostrowsky, 0.;Plenchette, A. Tetrahedron Lett. 1974,779. (6) For a representative example see: Rossi, R.; Carpita, A,; Gaudenzi, L.; Quirici, M. G. Gazz. Chim. Ital. 1980,110,237.
0022-3263/95/1960-4595$09.00/0
stereochemistry of the allylic partner is often lost (Scheme 1). While cross-coupling of y , y-disubstituted allylic compounds generally proceeds with high stereo- and regioselectivity, similar reactions with y-monosubstituted analogs give rise to mixtures of isomers (i-iii). Superior selectivity in palladium-catalyzed reactions involving y ,ydisubstituted allylic compounds is likely due to steric effects in the resultant n-allylpalladium complex. In the currently accepted mechanism of isomerization, n-allylpalladium species are postulated to exist in equilibrium with a-bonded counterparts. Rotation about the CZC3 bond in the a-bonded complex followed by formation of a n-allylpalladium intermediate results in isomerization of the allylic double b ~ n d . ~Presumably, ,~~ greater steric repulsion a t C3 disfavors formation of a a-bonded palladium-C3 intermediate, essential for E to 2 interconversion (Scheme 2). In the case of direct coupling of vinyl cuprates with allylic chlorides the main problem is one of regioselectivity. In cases where the allylic substrate is either unsubstituted or monosubstituted both a- and y-attack occur (Scheme 1). Recently, a new palladium(0) cross-coupling strategy was developed which showed promise as a stereoselective route to 1 , 4 - d i e n e ~ .It~ was demonstrated that isomerization in y-monosubstituted allylic substrates during palladium-catalyzed cross-coupling with E-vinyl organometallic reagents could effectively be eliminated by substitution of the y-hydrogen in the allylic coupling (7)(a) Miyaura, N.;Yano, T.; Suzuki, A. Tetrahedron Lett. 1980, 2865.(b) Negishi, E.;Chetterjee, S.; Matsushita, H. Tetrahedron Lett. 1981,3737.(c) Matsushita, H.; Negishi, E. J . Am. Chem. SOC.1981, 103,288.(d) Matsushita, H.; Negishi, E. J . Org. Chem. 1982,47,4161. (e) Matsushita, H.; Negishi, E. J . Chem. SOC.,Chem. Commun. 1982, 160.(0 She@, F. K.; Stille, J. K. J . Am. Chem. SOC.1983,105,7173. (g) Temple, J. S.; Schwartz, J. J . Am. Chem. SOC.1980,102,7382.(h) Hayashi, Y.; Riediker, M.; Temple, J. S.; Schwartz, J . TetrahedronLett. 1981,2629.(i) Negishi, E.; Chatterjee, S.; Matsushita, H. Tetrahedron Lett. 1981,3737.(i)Fen-Tair; Negishi, E. TetrahedronLett. 1986,2177. (8)(a)Black, D. St.C.; Jackson, W. R.; Swan, J. M. Comprehensive Organic Chemistry; Pergamon Press: New York, 1979;Vol. 3,pp 11351177.(b) Maitlis, P. M.; Espinet, P.; Russell, M. G. H. Comprehensive Organometallic Chemistry; Pergamon Press: New York, 1982;Vol. 6, p 249. (c) Collman, J. P.; Hegedus, L. S.; Norton, J. R.; Finke, R. G. Principles and Applications of Organotransition Metal Chemistry; University Science Books: Mill Valley, CA, 1980;pp 417-419. (d) Faller, J.W.; Mattina, M. J . Inorg. Chem. 1972,11,1296.(e) Oslinger, M.; Powell, J . Can. J . Chem. 1973,51,275. (9)(a) Hutzinger, M. W., Ph.D. thesis, Simon Fraser University, 1991.(b) Hutzinger, M. W.; Oehlschlager, A. C. J . Org. Chem. 1991, 56, 2918.
0 1995 American Chemical Society
4596 J. Org. Chem., Vol. 60, No. 14,1995
Hutzinger and Oehlschlager
Scheme 1. Palladium-Catalyzed Cross-Coupling of y-Monosubstituted Allylic Substrates with Vinyl Organometallic Reagents
M*
R,
X = CI, OAC M = RZAI, RZB, RZn
Rl
A
Ib
I
7
iii
Rz
Scheme 2. Double Bond Isomerization in mAllylpalladium Complexes
(28 : Isomers
f'
R,
R2A
Pd
/?
R2
iii
Scheme 3. y-Substitution in Allylic Substrates with a Ph(MehSi Group as a Strategy to the Stereospecific Synthesis of 1,4-Dienesa
3 ie
-
O1 n-BuLi, THF, -78 W 3 0 min, (CHzO), (1.3 equiv), -78 "C rt, 12 h, 85%; (b) Ph(Me)zSiZnEtzLi (3 equiv), CuCN (2%), THF, -78 "C rt, 12 h, 83%; (c) PPh3, CCWCH3CN (l:l), d 4 5 min, 81%; (d) DIBAL-H, hexane, 50 "C/2 h; (e) 4 (5 equiv), Pd(PPhs)r, THF, rU30 min, 88%; (0 n-BudNF, DMF, reflud4 h, 85% (by GC).
-
9 72)
a Pd(PPh3)r (lo%),THF, 60 "C/2 h, 73%; (b) n-BmNF (excess), DMF, 60 " W . 5 h; (c) determined by GC/MS; (d) GC ratio.
ii
Rl
Scheme 4. Trial Synthesis of (62,9Z)-Heptadeca-8,9-diene (9)"
partner with a Ph(Me)zSi group (Scheme 3). The stereochemical integrity of the allylic double bond was maintained throughout the coupling sequence yielding 1,4diene, 5, containing a vinyl Ph(Me)zSi functionality. Replacement of the trialkylsilyl moiety by hydrogen afforded the desired 2,EE-1,4-diene6. Desilylation occurred under conditions that tolerated alcohols, aldehydes, and acetates, commonly found in
pheromones. Thus, assembly of 1,Cdienic pheromones could, in principle, be accomplished via routes in which the final step from precursors already contained unprotected functionalities. Both Ph(Me)sSi and BwSn can act a s bulky hydrogen surrogates. In the present work we show that for stereoselective synthesis of 1,kdienes the tributylstannyl group is preferred. If BuaSn is substituted in the y-position of an allylic chloride the regioand stereoselectivity of palladium(0) catalyzed crosscoupling of vinylalanes and direct coupling of vinyl cuprates is increased to the point t h a t these couplings become useful reactions The strategy is applied to the synthesis of two 1 , l d i e n i c pheromones. Syntheses of Model 2,2-1,4-Dienes. While crosscoupling reactions of y-silyl substituted allylic chlorides with E vinyl organoalanes proceeded smoothly a t room temperature, more forcing reaction conditions were generally required in cross-coupling reactions involving more sterically congested 2-vinyl organometallic reagents. Thus, cross-coupling of 3 with (2)-nonenyldiethylalane, 7,yielded 1,4-diene 8 in 73% yield upon heating for 2 h a t 60 "C (Scheme 4). Although stereospecific assembly of the desired silylated 1,Cdiene 8 could be achieved by this method, subsequent desilylation afforded a mixture of isomers in addition to the desired 1,6diene 9. In light of this difficulty, attention was focussed on cross-coupling reactions of allylic substrates in which the y-silane was substituted by a trialkyltin moiety. It was hoped that replacement of tin with hydrogen in the coupled product could be achieved under more mild reaction conditions that would leave the geometry of the double bonds intact. To examine this possibility we required a y-trialkylstannyl substituted allylic chloride such a s 13. Synthesis of 13 was initially carried out by a procedure similar to t h a t used in the preparation of 3. Stannylzincation of propargylic alcohol 1 yielded 12 in good yield and high isomeric purity. Formation of appreciable amounts of tin byproducts which complicated workup and purification made this method unsuitable for multigram synthesis. It was found that 12 could be prepared more conveniently via 10 by reduction of 11 with DIBAL-H (Scheme 5). Ester 11 was obtained in excellent yield, high stereoselectivity, and relatively free of tin byproducts by stannylcupration of 10. Subjecting 12 to usual chlorination conditions (PPhB, CC1&H&N)21 did not give the corresponding allylic chloride 13 but yielded the destannylated product l-chloro-2(2)-octene. It was speculated that
J. Org. Chem., Vol. 60,No. 14,1995 4597
Stereoselective Synthesis of 1,CDienes
Scheme 5. Synthesis of Allylic Chloride 1301
Scheme 6. Destannylation of (6E,9Z)-6-(Tri-n-butylstannyl)heptadeca-6,9-diene
CH,(CH2)4-R p
-
(17)"
H 10: R = C(0)OMe 17
d C
la
12:X=OH 13: X = CI
C H d C H h ~ ( C H , ) & % 9
THF, -78 "C/30 min, methyl chloroformate, -78 "C -equiv),n-BuLi, 15 min, 97%; (b) n-BusSnLi equiv), CuBrDMS (1.3 THF, -78 W30 min, 10,-78 "C/1 h, MeOH (excess), -78 "C - 12 h, 91%; (c) DIBAL-H (2.4 equiv), THF, -78 "C/1 93%;(d)N-chlorosuccinimide (1.2 equiv), DMS (1.4 equiv), CH2C12, a
rt,
(1.3
rt,
h,
0 "C/10 min, 12,0 "C/1 h, 84%.
0
p-Toluenesulfonic acid (excess), THF, rt/30 min, 90% (by GC).
Scheme 7. Retrosynthetic Analysis of the Termite Trail Marker Pheromone 22 and the Leafminer Moth Sex Attractant 28 r
Table 1. Palladium-CatalyzedCross-Coupling of Allylic Chloride 13 with 2 Vinyl Organometallic Reagents" mBu3SnL CH3(CH2 )4~ c'
MA
(CH,),CH,
Pd(0) (cat)
*
n
17
reaction reagent (M) conditions yield, (%)b 1 Li[S-OMe-SBBN] (14) A 5 2 CpzClZr (15) A 4 3 EtA (7) B 42 4 BrZn (16) C 8oC a Reactions conducted in THF/ether (1:l): A = 60 "C/3 h; B = 50 "C/2 h; C = rt/30 min. GC yield. 16%of another isomer also formed. entry
~
destannylation was due to the formation of traces of acid since 13did form when this reaction was repeated under anhydrous conditione. Allylic alcohol 12 was readily converted to 13 in good yield under Corey halogenation conditions.1° Cross-coupling of 13with vinylboron 14, and vinylzirconium 15 reagents gave only traces of l,4-diene 17 (Table 1, entries 1 and 2). Conducting these reactions a t higher temperatures did not improve yields. Reaction of allylic chloride 13with 2-vinylalane 7 in the presence of a catalytic amount of Pd(PPh& afforded 1,bdiene 17 in moderate yield (Table 1,entry 3) while reaction with vinylzinc reagent 16 afforded 17 in 80% yield (Table 1, entry 4). Unfortunately, when produced by reaction with 16 formation of 17 was accompanied by 16% of another isomer, rendering this process unsuitable in synthetic applications requiring stringent control of stereochemistry. Stereospecific replacement of the trialkyltin moiety by hydrogen in 1 7 could be achieved under mild acidic conditions. Thus, treatment of 17 with excess p-toluenesulfonic acid in THF/MeOH gave the unisomerized diene 9 in excellent yield (Scheme 6).
Synthesis of the Termite Trail Marker Pheromone 22 and the Leafminer Moth Sex Attractant 28. Retrosynthetic analysis of the termite trail marker pheromone 2211 and the leafminer moth sex attractant (10)Corey, E. J.; Kim, C. U.; Takeda, M. Tetrahedron Lett. 1972, 4339.
28 via disconnection of an allyl-vinyl bond connecting the diene leads to a synthesis requiring the chemistry outlined above. Incorporation of a trialkylstannyl group a t the y-carbon in the allylic coupling partner 13 was expected to ensure stereospecific coupling (Scheme 7). Preparation of the 2-vinyl organometallic fragment required in the synthesis of the termite trail marker pheromone 22 proceeded from the tetrahydropyranyl ether of 1-butynol 18, which was initially converted to 19. Hydroboration of alkynyl iodide 19 with disiamylborane,12J3followed by treatment with glacial acetic acid a t rt, furnished 20 in respectable yield (Scheme 8). Cross-coupling of 13 with the 2-vinylalane derived from 20 afforded diene 21 in 51% yield. Tri-n-butyltin and THP groups were readily removed in a single step by stirring 21 in an acidified (p-toluenesulfonic acid) solution of THFMeOH ( l : l ) , affording pheromone 22 in 27% overall yield. The 2,Zgeometry was confirmed by lH decoupling which revealed vicinal vinyl hydrogen cou(11)(a) Matsumura, F.; Jewett, D. M.; Coppel, H. C. J. Econom. Entomol. 1972,65, 600. (b) Zhu,Yu-Xin; Liu, Ling-Yu. Hua Hsueh Tung Pa0 1980,530, 528. (12) Brown, H. C. Organic Synthesis via Boranes; Wiley Interscience: New York, 1975; p 100. (13)Corey, E. J.; Cashman,J. R.; Thomas,M.; Eckrich,T. M.; Corey, D. R. J.Am. Chem. SOC.1985, 107, 713.
4598
J. Org. Chem., Vol.60,No.14,1995
Scheme 8. Synthesis of the Termite Trail Marker Pheromone, (3Z,6Z)-Dodeca-3,6-den-l-ol (22)" R1
=
p
R2
2 R-OTHP
R, = H; R2 = OH
Scheme 9. Synthesis of the Leafminer Moth Sex Acetate (28)= Attractant, (4E,7Z)-Trideca-4,7-dienyl a OR - P O H
-
20: R = I
18: Rf = H; R2 = OTHP
bc
Hutzinger and Oehlschlager
-
dCR = Et2Al
bC
23: R = H 24: R = THP
DOTHP --I c
19: R, = I ; R2 =
R25: R = n B u 3 S n
ER
n-Bu3Sn CH3(CHz),-OTHP
= 2-thienyl(CN)Cu
\13
21
e
'I a Dihydropyran (excess), CHZC12, p-toluenesulfonic acid (cat.), 0 W10 min and then rt/l h, 92%; (b) n-BuLi, THF, -78 "C/10 min, 12, -78 "C/10 min and then r t / l O min, 92%; (c) 2-methyl-2butene, BH3,DMS, neat, 0 "C/2 h, 19,THF, rt/2 h, glacial acetic acid, rt/2 h, 56%; (d) t-BuLi (2 equiv), ether, -70 "C/30 min and then -30 W30 min, EtAC1, THF/ether (l:l),-30 "C/15 min; (e) 13, Pd(PPh& (lo%), THF/ether (l:l),50 "C/2 h, 51%; (0 p toluenesulfonic acid (excess), THF/MeOH (l:l), rt/30 min, 77%.
pling for both double bonds was 10.5 Hz, characteristic of Z double bonds. l4 The synthesis of 2815was envisioned as proceeding by direct coupling of a n E-vinyl cuprate and an allylic chloride such as 13 or its destannylated analog. Such couplings are attended by the same regio- and stereochemical problems i n t h e allylic coupling partner as the palladium catalyzed cross-couplings illustrated above. Access to the required E-vinyl cuprate commenced with conversion of 3-pentyn-1-01 to 4-pentyn-1-01, 23, via a zipper reaction in 78% yield.27 The latter was protected as the T H P derivative 24 and reacted with n-BuaSn(PhC=C)zCuLiz-LiI to give 25 in 78% yield and 96% isomeric purity. Recent work in this laboratory has shown that copper reagents of this composition react with l-alkynes to yield l(E)-(trialkylstanny1)alkenes('95%) (Scheme 9).9aJ6Transmetalation of 25 to a vinylcuprate followed by reaction with allylic chloride 13 gave 1,4diene 26 in moderate yield and high isomeric purity. Cross-coupling of this vinylcuprate with l-chloro-2(Z)octene gave an isomeric mixture of coupled product^.^" As in the case of the synthesis of 22,removal of tri-nbutyltin and T H P groups was accomplished in a single step by stirring 26 in a solution of MeOH and THF containing excess p-toluenesulfonic acid. Acetylation of alcohol 27, under standard conditions, afforded t h e desired pheromone 28,in 31% overall yield. The 'H NMR spectrum of 28 exhibited resonances attributable to vinyl hydrogens on two different double bonds. lH Decoupling experiments revealed the presence of a trans coupling of 16 Hz.14Although the complexity of the second vinyl resonance did not allow measurement of a coupling constant, its width (12.5 Hz) suggested the presence of a 2-double bond.14 The use of dimethylphenylsilyl and tributylstannyl groups as y-hydrogen surrogates in allylic partners of (14) Silverstein, R. M.; Bassler, G . C.; Morril, T. C. Spectrometric Identification of Organic Compounds; John Wiley & Sons: New York, 1981; p 235. (15) Voerman, S.; Herrebout, W. M. Ent. Erp., Appl. 1978,23,96. (16)These compounds were stored at 4 "C for several months without isomerization or decomposition.
Li (6.5 equiv), diaminopropane, rU.5 h, t-BuOK (4 equiv), rt/ 30 min, 3-pentyn-1-01, rt/2 h, 78%; (b) dihydropyran (2 equiv), CHZC12, rt/45 min, 94%; (c) n-Bu&h(PhC=C)zCuLiz-LiI (2 equiv), THF, 24, -30 "C 0 "C, 1h, 78%; (d) lithium 2-thienylcyanocuprate, MeLi, THF, -10 W 1 0 min, 25, 0 W1.5 h; (e) 13,-78 rt, 12 h, 55%;(f') p-toluenesulfonic acid (excess), MeOHPTHF (1: 11, d 3 0 min, 89%;(g) pyridine, acetic anhydride, rt/45 min, 92%.
-
-
allyl-vinyl cross-coupling reactions significantly improves stereoselectivity.
Experimental Section General M e t h ~ d s . GC ~ ~ yields J ~ were determined by using hexadecane as an internal standard and calculated according to the formula: gl = A1/A2 x RRF x gz @ I = grams of product; g2 = grams of ISTD.; A1 = area under product @I) peak, A2 = area under ISTD. ( 9 2 ) peak; RRF = relative response factor, Rf,/Rf,). Rf (gx/A,) values were determined for solutions containing a known mixture of gl and gz. An average value for solutions of varying concentration was used. Calculations and analyses were performed on the same gas chromatograph under identical operating conditions. 2-Octyn-1-01(I). This compound was prepared in 85% yield from l-hepytne according to a literature procedure.ls Distillation under reduced pressure afforded 1 as a clear liquid: bp 51 "C/0.25 mmHg (lit.1991 "C/12 mmHg). 3-[Dimethyl(phenyl)silyll-2(E)-octen-1-01 (2). This compound was prepared in 83% yield from propargylic alcohol 1, according to a literature procedure.20The product was purified by flash chromatography (SiOz, 10% EtOAc in hexanes) to afford 2 as a colorless liquid. IR (vapor) 3061(m), 2937(s), 2868(m),2361(m),2336(w), 1425(w),1375(w),1256(m), 1195(w), 1109(m), 1026(m) cm-l; 'H NMR 6 7.46-7.34 (5 H, m), 6.09(1H,t,J=6Hz),3.96(2H,q,J=6Hz);2.12(2H,t,J = 7 Hz), 1.27-1.09 (6 H, m), 0.93 (3 H, t, J = 7 Hz), 0.24 (6 H, s ) ; mass spectrum (EI) 262 (M+, < 0.51, 247(3),229(1),205(1), 185(2), 173(2), 152(3), 137(100), 136(11),121(11), 105(10), (17) Still, W. C.; Kahn, M.; Mitra, A. J . Org.Chem. 1978,43,2923. (18)Brandsma, L. Preparative Acetylenic Chemistry; Elsevier Pub. Co.: New York, 1971; p 25 and 69. (191 Egmond, G. J. N.; Pabon, H. J. J.;Van Dorp, D.A. Rec. J.Royal Netherlands Chem. SOC.1977,96, 172. (20) (a) George, M. V.; Peterson, D.T.; Gilman, H. J . Am. Chem. SOC.1960, 82, 403. (b) Okuda, Y.; Wakamatsu, K.; Tiickmantel, W.; Oshima K.; Nozaki, H. Tetrahedron Lett. 1986,4629. (c) Wakamatsu, K.; Nonaka, T.; Okuda, Y.; Tiickmantel, W.; Oshima, K.; Utimotto, K.; Nozaki, H. Tetrahedron 1986,42, 4427.
Stereoseledive Synthesis of 1,4-Dienes
J. Org. Chem., Vol. 60,No.14,1995 4699
91(6), 75(33). Anal. Calcd for Cld32sOSi: C, 73.27; H, 9.91. Found: C, 73.60; H, 10.19. l-Chloro-3-(dimethylphenylsilyl)-2(E)-octene (3). This compound was prepared in 81%yield from allylic alcohol 2, accordingto a literature procedure.21 The product was purified by flash chromatography (Si02, hexanes) to afford 3 as a colorless liquid: IR (vapor) 3200(w),3065(m),2964(s), 2937(s), 2887(m), 2361(w), 1256(s), 1105(m), 818(s)cm-l; 'H NMR 6 7.48-7.38 (5 H, m); 5.97 (1H, tt, J = 7.5 Hz; 1Hz); 4.13 (2 H, dt, J = 7.5 Hz;0.5 Hz); 2.15 (2 H, t, J = 7 Hz); 1.38-1.22 (4 H, m); 1.21-1.14 (2 H, m); 0.90 (3 H, t, J = 7 Hz); 0.26 (6 H, s); mass spectrum (EI) 280(M+, < 0.5), 265(5), 224(3), 209(2), 196(4), 187(3),173(4), 155(62),145(5), 135(100), 121(18), 105(171, 93(29), 67(26), 54(12). Anal. Calcd for Ci6HzsC1Si: c, 68.57; H, 8.93. Found: C, 68.82; H, 8.90. (sE,9E)-6-(Dimethylphenylsilyl)heptadeca-6,9-diene (5). To a stirred solution of Pd(PPh& (0.21 g, 0.18 mmol) in THF (30 mL) was added at rt, via syringe, a solution of allylic chloride 3 (0.5 g, 1.8 mmol, 2 mL THF) followed by a solution of vinyl alane 4 [prepared according to a literature p r ~ c e d u r e l ~ ~ (9 mmol in hexanes). The reaction was quenched after 30 min by slow addition of HCl(3 N, 20 mL). The aqueous layer was extracted with hexanes (2 x 50 mL) and the combined organic extract filtered through Celite, dried (MgS04), and concentrated in vacuo t o give a crude oil which was purified by flash chromatography (Si02, hexanes) to afford 5 (0.58 g, 88%)as a colorless oil: IR (vapor) 2964(m), 2934(s), 2864(m), 1460(w), 1355(w), 966(w), cm-l; lH NMR 6 7.57-7.30 (5 H, m); 5.82 (lH, t, J = 7 Hz); 5.47 (1H, dt, J = 15 Hz; 6 Hz); 5.38 (1H, dt, J = 15 Hz; 6 Hz); 2.84 (2 H, dd, J = 7 Hz; 5 Hz); 2.15-2.03 (2 H, m); 2.03-1.97 (2 H, m); 1.28-1.12 (16 H, m); 0.90 (3 H, t, J = 7 Hz); 0.85 (3 H, t, J = 7 Hz);0.37 (6 H, 8 ) ; mass spectrum (EI) 370(M+,l),292(1),271(2), 234(12), 208(1), 194(l),173(1), 159(1), 152(2), 145(2), 135(100), 121(16), 107(6), 91(3), 79(3), 59(3), 43(6). Anal. Calcd for C25H42Si: C, 81.08; H, 11.35. Found: C, 80.83; H, 11.60. (GZ,SE)-Heptadeca-6,9-diene (6). To a solution of 5 (0.02 g, 0.05 mmol) in DMF (10 mL) was added n - B d F (0.1 mL, 1M/THF, 0.1 mmol). The mixture was refluxed 4 h, cooled to rt, and diluted with hexanes (5 mL). Gas chromatographic analysis revealed that diene 6 had formed in 85%yield. The solution was washed with brine (3 x 50 mL), dried (MgSOd), and concentrated in vacuo t o give a yellow oil. A n analytically pure sample of 6 was obtained by preparative TLC (SiOd AgNO3 (20%), hexanes): IR (vapor) 3018(w), 2966(s), 2866(m), 1460(w),1385(w),1350(w),966(w), 714(w) cm-l; 'H NMR 6 5.47-5.31 (4 H, m); 2.72 (2 H, t, J = 6 Hz); 2.01 (4 H, q, J = 7 Hz); 1.39-1.16 (16 H, m); 0.87 (6 H, t, J = 7 Hz); 13CNMR 6 130.9, 130.6, 128.4, 127.9, 32.5, 31.8, 31.5, 30.8, 30.4, 29.6, 29.5,29.3,29.1,27.0,22.5,22.3,13.9; mass spectrum (EI)236(M+,15), 152(4), 151(3), 138(10),124(21), 110(40),96(57), 95(67), 83(21), 81(95), 79(39), 67(100), 55(34), 42(34). Anal. Calcd for C17H32: C, 86.36; H, 13.64. Found: C, 86.22; H, 13.76. (6E,9Z)-6-[Dimethyl(phenyl)silyllheptadeca-6,9-diene (8). To a solution of vinylalane 7 (1.1mmol) in Et2O/ THF (l:l, 4 mL) were added allylic chloride 3 (0.174 g, 1mmol) and Pd(PPh& (0.1g, 0.1 mmol) at rt, and the yellow solution was heated t o 60 "C for 2 h. The solution was diluted with aqueous NH4Cl (100 mL) and this mixture extracted with hexanes (2 x 30 mL). The combined organic extract was dried (MgSO1) and concentrated under reduced pressure. The resulting crude oil was purified by preparative TLC (SiOd AgN03 (20%),hexanes) to yield 8 (0.22 g, 73%) as a colorless oil: lH NMR 6 7.55-7.43 (2 H, m), 7.38-7.28 (3 H, m), 5.77 (1 H, t, J = 7Hz), 5.45-5.32 (2 H, m), 2.85 (2 H, t, J = 6.5 Hz),2.13-2.00 (4 H, m), 1.34-1.06 (16 H, m), 0.83 (3 H, t, J = 7 Hz), 0.76 (3 H, t, J = 7 Hz),0.28-0.25 (6 H, m); 13CNMR 6 139.4,134.0, 130.5, 128.7, 127.7, 127.6,32.2,31.9,29.9,29.7, 29.3, 29.2, 27.3, 27.1, 22.7, 22.4, 14.1, 14.0, -2.6; mass 234(4), 152(1),137(5),136(14),135spectrum (EI)370(M+,
